1. Technical Field
The invention relates to an acoustic shock protection device, and more particularly to acoustic shock protection device with a plurality of threshold gain values for a compressor and a method thereof.
2. Related Art
Abrupt, unexpected, and high-level sound can cause acoustic shock, a physiological and psychoacoustic injury to telephone headset/handset users. Since this type of injury is not related to a malfunctioning equipment, acoustic shock protection (ASP) must be handled in the end of the signal processing block where the final output signal is prepared to play back. Acoustic shock protection is designed to protect telephone headset/handset users from the source of acoustic shock.
An audio compressor may be used to adjust the signal level of an audio signal and to prevent abnormal loudness in a receiver path of a communication device. It is desirable to maintain audio signal levels within a prescribed range to avoid signal distortion and to enhance the audibility. The audio compressor can function as a noise suppressor for low amplitude signals and as a compressor for high amplitude signals.
However, commercially available audio compressors may not be designed to protect the user from acoustic shock signals in a receiver of the communication device. As a result, these audio compressors cannot pass the objective acoustic shock protection test requirements defined by the 3rd Generation Partnership Project 2 (3GPP2) standardization group, for example. Moreover, these audio compressors are not able to sufficiently suppress some particular tone signals generated by corrupted Code Excited Linear Prediction (CELP) vocoder packets or other corrupted packets.
Therefore, there is a need of a new acoustic shock protection device in the art, that could sufficiently suppress the particular tone signals generated by corrupted packets; protect the user from long time loud sound of any kind; prevent the acoustic shock in the receiver and achieve the test requirements defined by 3GPP2.